The present invention relates to a method and apparatus for classifying color originals from which color images are reproduced and more particularly to a method and apparatus for classifying color originals into at least color photographs and another color articles such as color printed articles, letters, illustrations, color art graphics and paintings according to their reflection densities.
In reproducing color images from color originals, color image reproducing machines such as electronics color image reproducing systems, ink-jet color printers, laser color printers, photographic color printers using reverse color papers or diffusion transfer type photosensitive materials, or heat sensitive copying machines, it is essential to reproduce a color image not only with proper color density but also with proper color balance. Generally used as color originals from which color images are reproduced are color photographs and color printed articles. When reproducing these color originals, even though same reproducing conditions are selected, the reproduced images tend to have different color densities and/or color balances owing to the differences between coloring materials for photographs and color printed articles or between the relative luminosity and the spectral sensitivity of image reproducing materials. For example, cyan and magenta inks used in making color printed articles have spectral density distributions widely overlapping on each other. In color image reproducing machines for making finished color images from color printed articles, an image reproducing condition is selected which restrains the density of magenta because color printed articles generally have a relatively high magenta density. When reproducing color images from color photographs using the reproducing conditions selected for color printed articles, the reproduced image tends to be too low in magenta density, resulting in a green tinted image.
In attempting to eliminate this undesirable color tint, the conventional color image reproducing machines are adapted to allow variance in the image reproducing conditions, such as the ratio of light components, by adjusting the three primary color filters, the exposures, the charging amounts, the development bias or the like according to the color originals, namely color photographs or color printed articles. For reproducing color images from color originals by the use of such conventional color image reproducing machines, an operator visually classifies the color originals into photographs and color printed articles and, according to the classified color originals, selects proper image reproducing conditions by operating condition selection keys.
One problem associated with the conventional color image reproducing machines is that the operator has to examine color originals for visible features such as the existence of printing dots. Because of recent advances in color printing technology, it is hard to visually determine the difference in image features between color photographs and color printed articles for, in particular, non-skilled operators.